Platelets and von Willebrand factor are key components in acute ischemic stroke clots

Background and Aims Previous studies assessing histological acute ischemic stroke (AIS) clot composition have characterised clot composition in terms of Red Blood Cell (RBC), White Blood Cell (WBC) and Fibrin composition. However platelets and platelet related factors such as von Willebrand are key components of coagulation and thus are likely also important in AIS clots. This study investigated the relationship between the expression levels of von Willebrand factor (vWF) and platelets (CD42b) in AIS clots. Method Sequential 3µm sections from AIS clots (n=55) were stained for platelets (CD42b) and vWF. Immunohistochemical staining for vWF (1:200) and CD42b (1:200) was performed using a Ventana Discovery autostainer. Expression levels were quantified using Machine Learning software (Orbital Image Analysis, Idorsia Ltd.). Descriptive statistics and correlation analysis (R2) for comparison were generated on GraphPad Prism. Results Platelets and vWF account for a significant proportion of the composition of the clots. The median (IQR) platelet content was 28.95% (14.26-40.28%) with a range of 1.72-89.44%. The median (IQR) vWF content was 18.59% (12.5-32.34%) with a range of 1.32-79.44%. A significant positive correlation (R2=0.4587) was found between the expression of platelets and vWF (F(1, 53)=44.90; p0.0001). Conclusions These initial results suggest that platelets and vWF are major components of AIS clots. Also the expression levels of both appear to be related to each other although variability has been observed. Understanding the relationships between various clot components will ultimately lead to better device design and or novel thrombolytic agents.